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I have a solar-powered scientific calculator that is at least 10 years old, and another that might be 20 years old. I never had to change their batteries once. Even after a few years in a drawer, they’re ready to go in an instant.

With digital calipers and micrometers, batteries will drain with use and self-drain over time.

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I was flipping through an industrial catalog when I came across Mitutoyo solar-powered calipers. Solar-powered calipers!

This makes a lot of sense for low-powered equipment.

I also have two solar-powered watches that never need replacement batteries, and they are always running, assuming they get enough sunlight to keep the internal battery charged.

This seemed pretty exciting, until I looked at Mitutoyo’s product specs. The calipers must be exposed to at least 60 lux of ambient lighting in order for them to be used continuously. That’s not a lot of light, but could complicate how and where the calipers are used or stored.

User reviews on Amazon confirm that the solar calipers perform best when exposed to bright lighting. Apparently, shadows cast over the face can cause the LCD display to dim or blank out.

Mitutoyo’s language about how the calipers can be powered even if uncharged at 60 lux suggests there’s an internal solar-charged battery or capacitor of sorts. In other words, you will only see best performance if the calipers are kept out and exposed to bright light to charge, or if they are only used in bright light.

In theory, these calipers would ease the frustrations associated with having to replace instrument batteries. In reality, it seems that the “solar battery” could lead to other frustrations, such as having to wait a few seconds for the calipers to charge up each time after taking them from a dark drawer.

10 Comments

I have an 8″ mitutoyo caliper, ive had it for years, its battery has only been replaced once, ive even left it on for months at a time, and it would still be on when i go to it. it is now 17 years old, sadly its last calibration date was in 99.

I’m a machinist and I own the 8″/200mm Super Solar Calipers. They work great, if you leave them out under fairly bright light for a half hour they’ll gain enough of a charge you can walk around in dark places for minutes and they’ll still work. I don’t know if the regular Solar Calipers have the capacitor inside.

I think for most people they’re an overkill item. I just enjoy my metrology equipment and they’re possibly the smoothest calipers I’ve ever used before once you tighten and back off on the gibs then wipe some oil on contact points on the rail.

I have a really old dial caliper by them. Still a fine instrument. It works fine with or without light. The batteries will go on forever 😉 Of course, a digital readout would be really great and not subject to the same kind of error or bad eyesight. Depends on how much you use it and the level of precision you need. Pretty neat to have solar, though.

The real hazard of battery powered instruments is not dead batteries, but corroded batteries. Like Mike, I prefer old school dial calipers. You can read the effect of varying pressure on the dial instead of flashing numbers whizzing by, and you can interpolate between the lines and approach Vernier type accuracy (with skill, patience and practice).

For home , I’ve used a 6 inch Starrett fractional dial caliper (1202F-6) for over 20 years and find it convenient and more than accurate/repeatable enough for woodworking and furniture-making. I like it because it’s graduated in 64ths – which fits well with most of my woodworking. I also have a newer Mitutoyo 500-96-20 which I also find useful – especially for metric fasteners etc.

Had a pair of older Mitutoyo Solar digital calipers and didn’t even know it as I looked forever for a battery door! Finally figured out they were solar after reading up about them, hadn’t even realized they made them.

Unless in bright light, the display was way too dim for use and wouldn’t hold enough of a “charge” to work unless it was under the bright light. No thanks – give me a battery powered caliper any day as the batts last forever and you can use them in relatively dimly lit areas.

They’ve been around for a long time but the body is more bulky and they’re spendy compared to the battery powered IP66/67 stuff. Never saw the need but my 12″ Mitutoyo IP66 calipers EAT both batteries over several months. Both pairs of my 6″ do not do this. As for “good old” dial calipers, that fine rack loves dust and chips. I’m never going back to mechanical unless working in a true clean room environment. A scale in epoxy makes SOO much more sense.

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